It is known to employ various reflective materials for safety and decorative purposes. These materials are extremely useful after dark when visibility under low light conditions becomes difficult.
Reflective materials are particularly beneficial when used in conjunction with protective clothing such as firemen's coats. Unfortunately, many of the available retroreflective materials are formed from substances which will not withstand the high temperature environments to which firemen or others may be subjected, thus relegating such materials to low temperature applications.
Firemen's clothing is illustrative of high temperature clothing. The materials and any trim attached thereto must meet strict standards established by the National Fire Protection Association (NFPA). With regard to heat resistance, materials must be able to withstand placement within a forced convection oven at a temperature of 500.degree. F. (260.degree. C.) for at least a five minute period. The materials must not melt, separate or ignite. With regard to flame resistance, the test material must withstand exposure to a direct flame, e.g. that emanating from a Bunsen burner, for a twelve second period. The test material must char less than four inches while not dripping or melting during exposure to the flame. Additionally, after the flame is removed, the test material must have an afterflame of less than two seconds. A material which passes the above tests regarding heat resistance and flame resistance is considered to define a fire-resistant structure. Although numerous materials are known which have superb reflective properties, it has been difficult to include such properties in a fire-resistant structure.
In order to create a reflective surface, the simple application of a reflective coating upon a substrate is perhaps the most common principle employed. Alternatively, the substrate might be formed from a highly reflective material, for example a polished metal. Another method of creating a reflective surface is the utilization of structures containing various formations which reflect the light rays impinging thereon, either principally as a result of the steepness of the angle at which the light ray impinges the surface or due to the inclusion of reflective coatings applied to the surface of the formations.
Retroreflective materials, e.g. those materials possessing the ability to reflect light rays in a substantially parallel path back toward the source of the light, are known in the art. One such material is sold under the trademark SCOTCHLITE by Minnesota Mining and Manufacturing Company and is comprised of minute glass spheres embedded in a matrix of synthetic resin. Also known in the art, is a class of retroreflective materials constructed of either glass or synthetic plastic resin containing cube corner formations molded into one surface thereof.
U.S. Pat. No. 3,684,348 discloses a synthetic plastic reflective material, marketed under the tradename REFLEXITE, containing a body portion having substantially smooth surfaces on opposite sides thereof and a large number of relatively minute cube corner formations which are closely spaced. Each cube corner formation contained three faces and a base adjacent the body portion with a side edge dimension said to be not more than 0.025 inches and preferably less than 0.010 inches. The body portion and the cube member portion are separately formed from essentially transparent synthetic resin and bonded into a composite structure. To optimize reflectivity, the composite material includes a reflective coating which is deposited upon the cube corner formations. This coating is often in the form of a metallic material which is further protected with a backing material to insure that the metallic coating is protected.
In addition to the use of reflective materials, it is often desirable to utilize luminous materials for the purpose of providing nighttime visibility in locations having little or no available light. A "luminous material" or "luminous composition" is intended to include any material or composition which has phosphorescent or fluorescent properties. Photoluminescent compositions have the ability to absorb energy from light which impinges upon it and then reemit the stored energy over a period of time in the form of light. Examples of luminous devices are shown in U.S. Pat. No. 1,373,783 which discloses a glass plate mounted in a metal holder and a layer of luminous powder compressed between the glass plate and the metal holder; U.S. Pat. No. 2,333,641 which discloses a luminous adhesive sheet or tape material; and U.S. Pat. No. 5,415,911 which discloses a photoluminescent and retroreflective sheet material.
U.S. Pat. No. 4,533,592 discloses a fire-resistant fabric having a reflective and retroreflective trim useful for firemen's clothing. The trim combines a fire-resistant base fabric upon which a fluorescent coating has been applied with a retroreflective material attached to cover a portion of the fluorescent coated area. The fluorescent coating is provided to achieve high day time visibility. The retroreflective sheeting is bonded to the fluorescent coating in a pattern such as a single center stripe or pairs of narrow stripes, with the proviso that at least 50% of the surface area remains as a glossy fluorescent exposed color coat for contrast and daytime visibility. The fluorescent coating disclosed therein is not photoluminescent and therefore does not enhance visibility in low light or no light conditions.
U.S. Pat. No. 5,648,145 discloses a fire resistant retroreflective structure which incorporates an array of rigid retroreflective elements having a first side and a second side. A transparent polymeric film is attached to the first side of the array of rigid retroreflective elements. A transparent fire resistant polymer outerlayer is in turn attached to the transparent polymeric film. A flame retardant layer is proximate to the second side of the array of rigid retroreflective elements. A fire resistant underlayer is further attached to the flame retardant layer. The transparent polymeric film can be bonded to the fire-resistant underlayer through the array of rigid retroreflective elements and the flame-retardant layer. In a particular method of assembly, pressure is applied to the retroreflective structure while exposing said structure to a suitable energy source such as ultraviolet light, heat or an electron beam. The bonded portions form the lines of a grid pattern and are significantly non-retroreflective as compared to the remainder of the retroreflective structure. Since the underlayer has no luminous or photoluminous properties, the grid lines do nothing to enhance visibility under any light conditions.
U.S. Pat. No. 5,300,783 to Spencer et al, the contents of which are herein incorporated by reference, discloses a flexible layered reflecting and luminous material which combines the advantages of a light reflective component and a luminescent component. The material includes a first layer of prismatic light reflective plastic material having an underlying surface formed with a plurality of minute prism-like formations projecting therefrom at regular spaced intervals and an overlying substantially smooth light transmissive surface. The material further includes a second layer of plastic luminescent material attached to the underlying surface of the prism-like formations. The layers are joined at a first region by heat sealing, ultrasonic welding, sewing, or stapling into a unitary structure. A second region is thereby defined at which the first layer and the second layer are physically distinct. In the second region, the layered material radiates luminescent light from the second layer through the underlying surface of prism-like formations and through the smooth light transmissive surface and simultaneously radiates reflected light from the prism-like formations through the smooth light transmissive surface of the first layer. Only phosphorescent light radiates from the first region. While possessing both micro prismatic reflective properties and luminous properties, the disclosure of Spencer et al fails to teach a fire-resistant structure that complies with NFPA guidelines for use on firefighter's protective clothing, or a method of producing such a structure, which incorporates both retroreflective and photoluminescent properties.
Thus, what is lacking in the art is a material defining a NFPA approved fire-resistant structure and method for its construction that provides enhanced retroreflective properties and simultaneously provides areas having enhanced photoluminescent qualities, thereby increasing a firefighter's visibility and safety under all lighting conditions, including "no-light" conditions.